Process of and apparatus for obtaining crystals



Nu. 6l6,82l Patented Dec. 27,. I898.

.1. Buck. PROCESS OF AND APPARATUS Fun OBTAINING CRYSTALS.

(Application filed Dec. 24, 1897.)

(No Mode'l.)

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4 UNITED STATES PATENT- OFFICE.

.TOHANNES BOOK, OF RADEBEUL, GERMANY.

PROCESS OF AND APPARATUS FOR OBTAINING CRYSTALS.

SPECIFICATION forming part of Letters Patent No. 616,821, dated December 27, 1898.

Application filed December 24, 1897. Serial No. 663,350. (No model.)

To aZZ whom it may concern.-

Be it known that I, J OHANNESBOOK, doctor of philosophy,a subject of the King of Prussia, Emperor of Germany, residing at Radebeul, near Dresden, in the Kingdom of Saxony, German Empire, have invented new and useful Processes of and Apparatus for Obtaining Large Well-Formed Crystals from Solution, (for which I have obtained patents in Germany, No. 95,183, dated November 29, 1896, and in France, No. 268,257, dated June 28, 1897,) of which the following is a specification.

The present invention relates to the extraction of organic or inorganic crystal'lizable substances from solution in the form of detached crystals, and is designed to enable such crystals to be obtained in well-formed large individuals on a large scale.

The invention is based upon the well-known method of crystallization in motion, according to which the formation of crystal individuals is caused by the continuous alteration of position or contact between crystals and a suitably-concentrated solution of the substance to be crystallized out. The known modes of carrying out this method are not able to give satisfactory results on the large scale for all products. The principal ground of this is the unsuitable Way of causing the motion or change of position. If as in one of the known modes of proceeding a stirring apparatus is caused to work in the solution provided with the crystals, then the crystals will be subjected to mechanical attacks during their growth-such as crushing, shivering, grinding, and the like-so that the even and undisturbed growth is prevented and neither well-formed nor large crystal individuals can be produced. This drawback is especially experienced when the difference of the specific weights between the crystals and the concentrated solution is considerable, because in this case the crystals always fall quickly to the bottom of the vessel, especially when they consist of large individuals. Similar attacks occur in the second mode, according to which the crystallization is elfected in a large vessel revolving on its axis. In this case a considerable proportion of the growing crystal in-' dividuals is forced continuously through the revolving of q the vessel beyond the falling angle, in consequence of which a continual falling over one another of the crystals takes place.

A method known as the conduction from below, according to which the solution is caused to pass upward through a high column of crystals, causes the said crystals to become continuously more and more pressed together by their own weight downward,whereby they are caused to grow together in crusts and other aggregations which inclose a good deal of solution or mother liquor.

The above-described drawbacks are obviated by the process or method hereinafter described, which constitutes the present invention.

- The crystals are arranged in a thin layer in a long extended vessel, such as a gutterlike or tubular Vessel. This vessel is mounted horizontally or slightly inclined. The solution for supplying those crystals, with the substance required for their growth or feeding solution, is caused to flow through the vessel in the direction of its long axis or transversely to the height of the layer with a slow motion. During this passage the vessel is given a seesaw or revolving motion transversely to the direction of the flow, and the solution flowing through is allowed to cool very gradually. The feeding solution will consequently pass in very thin streams between the crystals. combination with the very slow cooling, permits the surface attraction of the crystals to act to its full extent, but causes a separation at each point only to take place in a very small quantity, consequently at every section of the vessel uniformly. There is obtained, moreover, a to-and-fro alternating washing contact between the feeding solution and the crystals, whereby deposition in utmost thin layers is promoted, while the continuous changes of position between the crystals and the feeding solution, in combination with the uniform supply of the latter at the entrance end, does not allow of any growing together. In consequence of this combined action there is obtained a perfectly even growth of the separate crystals without any growingv together and taking up of fluid.

This fine division, in

By aid of the above-described process and 1 suitable adjustment of the conditions of operation--such as initial saturation of the feeding solution, suitable length and inclination of vessel, &c., to the peculiarities of the substance to be crystallized-it has become possible to produce on a large scale well-formed large crystal individuals not only of sugar candy, but also of soft substances-such as fuchsin, borax, soda, and the like-and of brittle substances, such as alum, sulfate of.

copper, citric acid, and the like.

The process can also be carried out for very soft as well as for very brittle crystals by providing the vessel with a soft chemically-indifierent and impermeable lining, such as asbestos, felt, india-rubber, and the like. As the remaining solution leaves the vessel at a certain concentration-11 e., a concentration corresponding to the temperature of exit-it afiords a very advantageous means for supplying the vessel with fresh quantities of substance by simply heating it up to the entrance-temperature and saturating it with the substance to be supplied to the crystals or by evaporating or otherwise concentrating it to the original saturation-point and cansing the resaturated solution to return into the vessel to serve anew as feeding solution. The dissolving medium can thus be allowed to move in a circuit, and it is only necessary in order to make the process continuous to replace the finished crystals removed from the vessel by the introduction of small crystals or by the new formation of crystals from the solution and to compensate the loss of dissolving medium.

On the annexed sheetis represented a specimen of apparatus for carrying out the invention.

Figure 1 is a perspective front elevation, and Fig. 2 the right-hand end view, the crystallization vessel being shown in cross-section.

The apparatus shown is one for continuous operation with oscillating motion of the crystallizing vessel. The crystallization vessel ct is in the form of a gutter of semicircular section, the lid of which, where such is required, consisting most suitably of covering-plates a, folding on one another, so that local observations may be taken. The said gutter is provided with an inlet?) and an outlet 0, both of which may be adjustable. To effect the oscillating movement,thegutter is suspended by means of links a from the cross-arms a of a shaft (0*, supported above revolubly in a bearing a, which shaft is coupled by means of an arm a in the usual manner with the rod a of the eccentric a of the driving-shaft a". The rotation of the said shaft 01, will consequently cause the shaft a to oscillate, whereby the gutter a is given a seesaw motion. The exit a is attached by means of reflexible tube 0 to the pump 19, which forces the exit liquor through the pipe 19' to the dissolving apparatusZorsaturatorprovided with heating apparatus 721. The outlet l of the saturator is connected by a flexible pipe Z2 with the inlet 1) of the gutter a.

Fig. 2 shows the gutter provided with a soft lining The movement or disturbance which is given to the crystals and solution while the the crystals are being formed is gentle and relatively slow, so as not to result in the crystals being so agitated among themselves as to be broken or ground to pieces.

What I claim is-- 1. The herein-described process of obtaining well-formed, large, individual crystals from a saturated solution, which consists in heating the solution, passing the hot solution slowly through a long, thin mass of crystals or like substance to those to be produced, and at the same time subjecting the solution and crystals to a gentle and relatively slow disturbance, and also to a gradual cooling, substantially as set forth.

2. The herein-described continuous process of obtaining well-formed, large, individual crystals from a saturated solution, which consists in heating the solution, passing the hot solution slowly through a long, thin mass of crystals of the substance being crystallized, at the same time subjecting the solution and crystals to a gentle and relatively slow disturbance and to a gradual cooling, uniformly withdrawing the weakened solution from the presence of the crystals, resaturating and reheating such withdrawn solution and repeatin g the above steps, substantially as set forth.

In an apparatus for producing large, well-formed crystals, the combination of a relatively long, closed vessel, an inletat one end, an outlet at the other end, a shaft a provided with cross-arms and arranged 1ongitudinally of said vessel, links connecting the said cross-arms and the vessel, and means for working the shaft a, whereby the vessel is rocked transversely of its longitudinal axis, substantially as set forth.

4. In an apparatus for producing large, well-formed crystals, the combination of a vessel in which the crystallization takes place, means for gently disturbing the same, and a soft fibrous lining applied to the interior of the vessel, substantially as set forth.

5. The combination of a relatively long,

narrow vessel having an inlet at one end 'and' JOI-IANNES 1300K.

YVitnesses:

HERNANDO DE So'ro, WILHELM WIESENHUTTER. 

